FIG. 1 shows an example of a conventional piezoelectric driving waveform generating circuit. As shown in FIG.1, it is composed such that to piezoelectric driving waveform generated in a reference waveform generating circuit, a current amplifying circuit supplies as much current as necessary.
In this case, given that piezoelectric driving voltage (piezoelectric driving waveform output terminal voltage) is Vpzt (FIG. 2(a)), collector current of transistor Tr1 is i1 (FIG. 2(b) collector current of transistor Tr2 is i2 (FIG. 2(c)), and high-potential side power source (high-voltage side power source) is Vh, energies P1, P2 to be generated at transistors Tr1, Tr2, respectively are given by: EQU P1=(Vh-Vpzt).times.i1 EQU P2=Vpzt.times.i2
which are represented by FIGS. 2(d), (e), respectively.
Since these energies generated are all heat generation from transistors, conventional devices cope with the situation by providing a high-rating transistor or heat sink. This prevents the devices from being miniaturized.